The Revolution of Train Control System in JAPAN
Masayuki Matsumoto
East Japan Railway Company
2-2-2 Yoyogi, Shibuya-ku, Tokyo 151-8578, JAPAN,
Tel : +81-3-5334-1245, Fax : +81-3-5334-1246 E-mail : [email protected]
1. Introduction
Abstract
The following report will introduce train control
systems applied in railway lines in Japan. The report
also will show that train control systems have been
developed and these are classified four levels from
“Level 0” to “Level 3”. We call these train control
systems “East Japan Train Control system” (EJTC).
“Level 0” system, the Automatic Train Stop device
(ATS-S), was introduced into Japanese National
Railways (JNR) to prevent train collision. This system
has been replacing with Pattern type ATS (ATS-P);
“Level 1” system. ATS-P was developed to eliminate
the weaknesses of the ATS-S.
The Automatic Train Control (ATC) system was
originally developed to support safe, super-high speed
railway transportation utilizing Japan’s Shinkansen
and introduced into conventional commuter lines to
shorten the train interval. However it was difficult to
realize efficient operations in high-density lines due to
limitations of existing ATC technology. Then the
D-ATC system (Digital and Decentralized ATC) had
been developed as “Level 2” system using ADS
technology. In D-ATC system, the device on each
train autonomously calculates permitted speed of each
train. This system is introduced to Keihn-tohoku Line
as D-ATC and Shinkansen Line as DS-ATC (Digital
Communication & Control for Shinkansen-ATC).
Recent remarkable progress in the field of
information technology makes possible a new train
control system where train itself detects its location
and communicates with other trains through radio
transmission. Therefore, we have been developing the
“Level 3” train control system called ATACS
(Advanced Train Administration and Communications
System). ATACS is the new train control system using
information technology and ADS technology. ATACS
prototype system is testing at Senseki Line in Tohoku
district for practical use.
0-7803-8963-8/05/$20.00 ©2005 IEEE
In the beginnings of railways there was no signaling
system. A station attendant showed the signal of go or
stop by gestures. But a man often makes mistakes, and
train accidents happened. Although drivers operate
trains in accordance with signals, there is a potential
for rear-end and head-on collisions, and other
accidents if signals are ignored or misread by drivers.
Signaling system prevent these accidents. Automatic
Train Stop (ATS) devices prevent these types of
accidents by stopping the train automatically when a
signal is showing stop. If the driver ignores the
warning from ATS, on-board equipment automatically
brakes and stops the train.
In the transportation and safety area, operations
have become very efficient as a result of the
systematizing of train operations, and introduction of
new automatic train stop devices (ATS-P). By using
digital information from a transponder, ATS-P
transmits information about signal aspects and the
distance to the next stop signal from the trackside to
the train and uses this information to generate a train
speed-checking pattern. ATS-P then evaluates whether
the driving speed is appropriate and automatically
applies the brakes when the situation is judged to be
dangerous.
Since the missing of a signal can lead to a serious
accident, it became necessary to install devices that
display the permitted speed and apply braking
automatically in accordance with the emerging
instruction on high speed line sections and high
density lines. This device is known as an Automatic
Train Control system (ATC). ATC was first introduced
on the Tokaido Shinkansen because it was thought that
conventional signals were difficult to see safely at
high speeds. Introduction of ATC has enabled safe
operations even when drivers misread the signal
aspect and the level of safety has been heightened
599
compared to the point control type ATS as it employs a
continuous control system. ATC is obligatory on line
sections with cab signal block systems. The ATC
on-ground equipment transmits signal currents for
controlling speeds in track circuits and the on-board
ATC equipment receives these signals. It shows
signals on-board and has a function for automatically
controlling braking according to signal aspects.
However, since ATC devices are based on
technology existing at the time the Tokaido
Shinkansen was built, they present many problems
including an inability to increase the number of trains.
The following is an analysis of the ideal form of ATC
as a train control system. The only thing necessary
to stop a train without running into the preceding train
is to know “the distance to the position where the train
must stop.” The information essential for this is “the
accurate position of the train” and “the position at
which the train should stop.” By reanalyzing the
actual objective of ATC, the basic function of the new
train control system emerged. In other words, the
groundside devices should only transmit information
on the position at which the train must stop and the
train should recognize its own position and calculate
the distance to the stopping point transmitted from the
ground. The train then should take curves, gradients
and such into consideration and apply appropriate
braking at the necessary time. This is the principle of
the new train control system (D-ATC) that we have
newly developed.
The present signaling system has a long history and
provides a fairly high degree of safety and at the same
time helps maintain a certain level of traffic utilization,
but on the other hand it has some problems.
Remarkable progress has been made recently in the
field of integrating mobile communication technology
and computer technology. It is hoped that the
introduction of mobile communication technology and
computer technology into the railway control system
will help minimize the wayside facilities and make
flexible repairs possible, thereby solving the problem
of high cost. Accordingly, efforts are being made to
develop a new railway control system called ATACS,
for which information technology (digital radio and
computer technology) is utilized and a new framework
of wayside and on-board functions has been adopted.
The report will introduce the train control systems,
technology used in this systems and future
developments.
The first passenger railway transport system began
to operate in 1830 between Liverpool and Manchester
in The United Kingdom. Afterward a signaling system
was adopted to improve safety and to cope with the
increase of traffic volume.
Progress of signaling technology has been
achieved by electronic communication technology. In
1841, it was installed at both ends of a tunnel of North
Midland Railway to make it possible to communicate
between both ends to prevent the entry of more than
one train in the tunnel at the same time. That is the
beginning of fixed block signaling, which prevents
train collisions. The track circuit, which detects a train
position, was invented in 1872. All of these devices
have been contributing to improve safety. Although
some modifications were adopted after their invention,
present signaling systems are based on principles
invented in the 19th century.
Various tests were carried out starting in 1921
during the pre-war Japanese Government Railways era.
A cab warning device, a predecessor to ATS, was in
use on the Yamanote and Keihin Tohoku Lines from
December 1954. Despite this, a major train collision
killing over 100 people still occurred on 3 May 1962
at Mikawashima Station on the Joban Line. This was
just after studies on a new cab warning device had
started, and the accident led to the decision to
introduce the ATS system - a system that adds a stop
function to the on-board warning device. The resultant
ATS was introduced on all sections of Japanese
National Railways (JNR) in April 1966. This device
was called ATS-S.
Development of the ATS-P was pursued as a result
of a derailment at Hirano Station on the Kansai Main
Line in 1973. It entered service for the first time in
March 1987 at some stations (Kusatsu, Kyoto, Osaka
and Nishi-Akashi) on the narrow-gauge Tokaido and
Sanyo Main Lines, and on express trains (hauled by
electric locomotive) after another derailment at
Nishi-Akashi Station on the Sanyo Main Line in 1984.
In September 1988, JR East established the first
phase of a construction plan that called for
introduction of ATS-P on the Chuo, Joban, and other
Lines. With the opening of the Keiyo Line on 1
December 1988, ATS-P was in use on an entire section
for the first time. A further train collision at
Higashi-Nakano Station on 5 December 1988 led to
the speeding up of the planned introduction, and
sections where the system was to be introduced were
also expanded (Chuo Line in 1989 and others since).
Use of it has currently spread to the principal line
2. Development of train control systems in
Japan
600
sections in the Tokyo Metropolitan Area, the Yamagata
Shinkansen and the Akita Shinkansen.
Concurrent with the opening of the Tokyo Olympics,
operation of the Tokaido Shinkansen Line commenced
between Tokyo and Osaka in October 1964. As
Shinkansen trains run at super-high speeds, the cab
signal system that sends speed signals to the driving
cab has been used since operation of the Tokaido
Shinkansen Line commenced. The ATC system is used
to automatically control train speeds in accordance
with those speed signals. The ATC is an important
piece of equipment that ensures safe, stable high-speed
transportation. In this ATC, the central ATC logic
device calculates permitted speed in each blocking
section and controls speed of all trains.
ATC was introduced on narrow-gauge lines when
through operations started between the JNR Joban
Line and the Chiyoda subway line in 1971. In 1981, it
was introduced on the Yamanote Line, Keihin Tohoku
Line and other sections as a safety measure after
repeated rear-end collisions at Funabashi, Nippori and
other JNR stations. The Joban Line ATC had been
renewed in 1999 and it uses single-level brake control
rather than the conventional multi-level brake control.
JR East decided in 2000 to develop and introduce a
new digitally operated D-ATC and DS-ATC taking
into account the facts that the present ATC needs to be
renewed. In the D-ATC, the central logic device
calculates each position to which a train can move
safely, and sends the information on positions to all
trains. On each train, the on-board equipment
calculates an appropriate braking pattern with the
information, and controls velocity of the train. That is,
in the new system, the device on each train
autonomously calculates permitted speed of the train.
DS-ATC was introduced to Hachinohe Shinkansen in
2002.12 and D-ATC was introduced to the
Keihin-Tohoku Line in 2003.12. and in the near future
DS-ATC will be introduced to the Tohoku and Joetsu
Shinkansen.
JR East is currently developing a train control
system that uses wireless communications, known as
ATACS. Present train control is performed in the
following manner. Train location is detected by
wayside signaling facilities, and according to train
location, train control signals are displayed to prevent
collisions between trains. However, this control way
requires an enormous number of facilities. That means
large construction and maintenance costs. Recent
remarkable progress in the field of information
technology makes possible a new train control system
where a train itself detects its location and
communicates with other trains through radio
transmission.
Therefore, we have been developing the new train
control system called ATACS. ATACS is the new train
control system using information technology and ADS
technology. The prototype system was tested last year
on the Senseki Line in Tohoku.
3. Classification of train control system
As described earlier, a train control systems have
been developed by the Japanese National Railways
and the East Japan Railway. As a result, accidents of
collisions of trains, rear-end collisions and so on have
decreased remarkably.
We classify train control systems into 4 levels, with
the overall name East Japan Train Control system
(EJTC). Each level’s system is used on appropriate
lines according to characteristic of the railway (Table
1).
Also, for these systems, the level is determined by
fixed block system or moving block system, train
detection by the track circuit or train position
recognition with an on-board system, information
transmission to on-board via the track circuit or by
radio, and so on. These are shown in Table 2
comparing with the characteristic of ETCS in Europe.
Table 1 Classification of EJTC
Level
EJTC
ATS-S : It sounds a bell or chime to encourage confirmation of
the signal and issues an alarm in the form of a red display when
Level 0 the train is approaching a stop signal. If the driver does not
confirm the situation within a set period (5 seconds), the brakes
are automatically engaged and the train will be stopped.
ATS-P : It doesn't require driver verification, and when the train
speed is approaching the danger speed pattern, it draws the
Level 1 attention of the driver by sounding an alarm. The system
engages the service brake at maximum power automatically
when the speed pattern is on the verge of the danger pattern.
D-ATC : The ground side should only transmit information on
the position at which the train must stop and the train should
recognize its own position and calculate the distance to the
Level 2
stopping point transmitted from the ground. The train then
should take the roadway curves, gradients and such into
consideration and apply appropriate braking.
ATACS : The ground controller in each area has such functions
as train location, interval control, switching control, level
crossing control and security for maintenance work. The radio
base station exchanges information with the on-board computer.
Level 3
The on-board computer controls brake according to control data
supplied by the ground controller and also transmits data on the
train location to the ground controller through the on-board
mobile radio station.
601
Table 2 Comparison of EJTC and ETCS
EJTC
Level 0
EJTC/ETCS
Level 1
EJTC
Level 2
Way side signal
Signaling system
Train detection
Transmission
to train
Transmission
to ground
Position recognition
EJTC/ETCS
Level 3
Cab signal
Block system
Fixed block
Moving block
By track sircuit
Train itself
Transponder (Balise+Loopcoil)
Wireless
Nothing
On-board
Point control
Continuous control
4. Level 0 (ATS-S)
Red lamp lights
Bell sounds
Speed
A block system secures safe train operation. Almost
all train control systems are based on it. In the railway
system, safety to secure the interval between trains is
based on the block system concept that only one train
can go into a block section.
In a block section where a train is present, a track
circuit detects the train, and some control device (relay
logic, ATS or interlocking system) turns the signal for
the section to Red. This status indicates that no other
train can go into the section so the train must stop
before the section. Signals of other sections, into
which a train can go, are Green or Yellow. They
correspond to the current permitted speed of the
section that is determined by the distance to the
section with the red signal. Fig.1 illustrates the
relation between the signal status of a section and the
position of a train. The block system used in ATS and
ATC is based on fixed block sections that consist of
track circuits and signal devices.
The ATS secures the braking operation even if a
driver is not able to brake. When a train approaches a
stop signal, the ATS warns the driver to confirm the
signal. The Automatic Train Stop device (ATS) sounds
a bell or chime to encourage confirmation of the signal
and issues an alarm in the form of a red display when
the train is approaching a stop signal. If the driver
does not confirm the situation within a set period (5
Yellow
Red
Slow down
Stop
Train Speed
5 seconds
Emergency brake
Normal
operation
Yellow
Red
Transponder
Fig. 2.
ATS-S system
Signal box
seconds), the brakes are automatically engaged and the
train will be stopped. When the confirmation takes
place, operations can continue under the discretion of
the driver (Fig. 2). However, mistaken handling has
been the cause of accidents and this is also a weakness
of the ATS-S.
5. Level 1 (ATS-P)
The ATS-P was developed to correct a weakness of
the ATS-S described before. By using digital
information from a transponder, ATS-P transmits
informatio n about signal aspects and the distance to
the next stop signal from the trackside to the train and
uses this information to generate a train speed
checking pattern. The train speed and this pattern are
then compared in a computer and the brakes are
engaged if the speed of the train is exceeding the
speed of the pattern. Unlike the ATS-S, it doesn't
require driver verification, and when the train speed is
approaching the danger pattern, it draws the attention
of the driver by sounding an alarm. The system
engages the service brake at maximum power
automatically when the speed pattern approaches the
danger pattern.
block section
Signal aspect transmission
Wireless
On-board antenna
Nothing
Control method
Green
ETCS
Level 2
Preceding train
Train detection
Fig.1. Block system and signal aspect
602
device that indicates permitted speed is located in the
driver’s cab on trains, and it continuously receives
information on the permitted speed transmitted from
ground equipment.
The central ATC logic device sends ATC signals to
track circuits. The ATC signal is information on the
permitted speed, and at the same time, it is used as a
train detection signal. The logic device can determine
the section on which a train is present by monitoring
the level of received ATC signal power because the
wheels of the train short the track circuits. Boundaries
of the track circuits and the pattern of permitted speed
are designed in order to sustain train’s headway, which
is necessary for train traffic control.
In the ATC system, the central ATC logic device
takes charge of most of the train interval control, and
on-board equipment only controls the braking of the
train according to instructions from the central device.
The conventional ATC improves security and traffic
efficiency but some problems still remain as listed
below.
(a) The braking control pattern is not smooth at the
boundary of a section, therefore the time of a braking
operation tends to increase, driving operability is bad
and the train interval cannot be shortened.
(b) The improvement of rolling stock performance
does not improve the efficiency of transportation
because the headway mainly depends on the permitted
speed and the boundary position of the section.
(e) Most equipment is placed in the central part of
the system and many cables are laid from the central
device to the track circuits, which is costly.
Permitted Speed Pattern
Speed
Service brake
Normal
operation
Warning of
approaching to
pattern
Yellow
Red
Transponder
Encoder
Fig.3. ATS-P system
Fig. 3 shows the overall structure and the speed
pattern and installation standards for transponders in
the case of block signals.
The ATS-P has several functions. It prevents signal
violation accidents for entry/exit block signals,
shunting signals related to main track and calling-on
signals. And it prevents accidents resulting from
exceeding speed limits on turnouts, curves and down
gradients. Moreover ATS-P increases signal aspect
efficiency for high braking performance trains. High-,
mid- and low-deceleration train information is
transmitted from on-board to the trackside. This data
is evaluated at the trackside and signals are controlled
accordingly.
The train ID and other information can be sent to
the trackside from on-board. This information can be
used for operational control of trains, control of level
crossings according to train speed, automatic public
announcements at stations, etc.
When the driver is operating the train at a level
equal to or below the speed pattern in the figure, the
brakes are not applied. The brakes are applied only
when the train operation exceeds the speed pattern.
To enable a train stopped ahead of the final
transponder to operate after the signal changes to
Caution or Clear, the speed pattern up to the signal is
set to a maximum of 10 km/h. In addition, if the train
passes the transponder at a stop signal, "Stop
immediately (service)" is received and the maximum
service brake is applied immediately and a speed limit
of 15 km/h is applied for 80 m from the transponder in
the forward direction.
6.2. D-ATC
An interval control is another concept of train
control. In this control method, a system recognizes
the distance between a train and a preceding train and
ensures safe train operation by controlling the speed of
Speed
Train Speed
Permitted Speed
6. Level 2 (D-ATC)
90
6.1. Conventional ATC
65
65
45
45
0
ATC-Device
Fig. 4 illustrates train speed control of a
conventional ATC system. In the ATC system, a signal
Fig.4. Conventional ATC system
603
these trains. In order to realize this interval control,
various new functions are required such as accurate
train location and high-speed communication between
trains and ground equipment.
In this manner, the major difference between the
D-ATC system and the conventional ATC is that the
D-ATC system is an on-board intelligent system. The
new system differs from the conventional system in
that each train autonomously calculates the
appropriate permitted speed with information on the
stop position transmitted from the central ATC logic
device (Fig. 5).
The following are the characteristics of the new
system.
(a) High-density traffic is possible as brakes are
continuously engaged up to the stop point using
pattern control.
(b) The ground facilities can be slimmed down and
made inexpensively due to the use of general
information equipment and a decentralized system.
(c) The system contains the flexibility of being able
to shorten the train headway without changing ground
equipment when rolling stock performance is
improved.
(d) Improved operability can be obtained by
indicating the train usage on routes to driver.
Consequently, the cost of the D-ATC system is less
than that of the conventional ATC and has also
enabled the train headway to be shortened to two
minutes from the two minutes and thirty seconds of
the conventional ATC systems. Also, construction
costs can be lowered by twenty percent compared to
traditional methods.
Further, both reliability and safety have been
improved and a figure of 10-12 has been secured for the
failure rate of the danger side as SIL 4 level.
East Japan Railway Company(JR East), has
developed a new Shinkansen D-ATC that utilizes
digital communications and control, officially called
DS-ATC. Reductions in arrival times and intervals
between trains can be realized as well. DS-ATC is
expected to contribute to safer, smother Shinkansen
transportation.
7. Level 3 (ATACS)
7.1. System configuration
The ideal form of interval control consisting of
trains knowing each other’s positions through wireless
communication between them also becomes possible.
JR East is currently developing this type of a train
control system that uses wireless communications
known as “ATACS.” ATACS is the new train control
system using information technology. The objectives
of ATACS are as follows:
(a) Cost reduction
Reducing construction and maintenance costs
(b) Flexibility for system changes
No need of improvement work when train speeds
are increased or headways shortened
(c) Improved safety
Closed-loop control and security for maintenance
work
A section of railway line is divided into several
control areas, in each of which a ground controller and
a radio base station are set up. The ground controller
in each area has functions such as train location,
interval control, switching control, level crossing
control and security for maintenance work. The
radio base station exchanges information with the
on-board computer. As the appropriate interval
between stations is determined according to the
service area covered by radio transmissions, several
base stations may be linked to the same ground
controller.
The on-board computer controls brakes according to
control data supplied by the ground controller and also
transmits data on the train location to the ground
controller through the on-board mobile radio station.
The first step in the control procedure is to determine
the accurate location of a train as measured by the
on-board computer. The initial position of a train is
input when the train passes balise put up on the system
boundary across which trains enter or exit.
Subsequently, the on-board computer keeps track of
the train location by detecting its speed and processing
the speed data. The train location is corrected when
the train passes a balise set at appropriate points (Fig.
6).
3. Its train position recognition
4.brake pattern occurrence
5.Brake control
1.Train detect
Train
Preceding train
Digital control signal
Digital train detect signal
Transmitter device
2.Stop position transmission
ATC-LAN
Logical controller
Fig. 5.
D-ATC system
604
Digital radio communication
4. brake pattern occurrence
authority) on the basis of data on the train location and
route of each train in the control area, and transmits
the findings to each train. Further, the on-board
computer determines the permissible distance of
running based on the limited movement authority and
the present train location. With braking performance
and track conditions (gradient, curve, speed limit, etc.)
taken into consideration, the on-board unit generates a
brake intervention curve which can cause the train to
stop at the limit of this permissible distance of running
and applies the brakes.
(b) Level crossing control
In ATACS, level crossings are controlled on the
basis of an exchange of data between trains and the
ground controller.
For adjusting train approach warning duration, the
train calculates estimated time of arrival at the level
crossing according to train performance and speed and
sends it to the ground controller by radio. The ground
controller activates the level crossing according to this.
After activating the level crossing protection, the
ground controller sends to the train, and the train
recalculates the brake intervention curve. If the level
crossing protection does not become active, the train
stops before the level crossing.
(c) Other function
There are other functions such as security for
maintenance work, switching control, bi-directional
distance control and temporary speed limits.
2. Train position
transmission
1. Train position
recognition
3. Its train position
recognition
5. Brake control
Logical controller
and Radio station
Fig. 6. ATACS system
The train location as detected by the system is
structured into the identification number of the ground
controller in the relevant control area, the virtual
blocks into which the control area is divided, and the
position within the relevant track block, and these data
are processed by the wayside and on-board computer.
Radio base stations are set up at intervals of three
kilometers or so based on the reach of radio
transmissions. To prevent radio interference between
adjoining radio base stations, waves of four different
frequencies are used alternately.
For on-board
operation, the frequency is so chosen as to be
receivable by the radio base station in each area.
Each base station needs to communicate with several
trains running in its area, assuming that it
communicates with each train on a one-second cycle.
Accordingly, one second is divided into several time
slots. An error may occur in the data during the
transmission.
Accordingly, the space diversity
system and the Reed-Solomon code for forward error
correction are adopted to improve the quality of
transmission.
7.3. ADS technologies of ATACS
In ATACS, the ground system is decentralized, and
each device is connected by a network. Each on-board
system does brake control autonomously by using the
limited movement authority that it has been given in
transmitted information by the ground controller. The
ground system is divided into a central control of
traffic system and a train control system, and it is the
composition which gives autonomously to each
equipment. As a result, it prevents a failure of some
equipment from affecting the whole system. And it is
possible to build a system step-by-step.
When a radio base station breaks down, an adjacent
radio base station backs it up autonomously, and
operation of the system is continued automatically.
7.2. Function
ATACS has many functions. Here, we describe the
main functions, train interval control and level
crossing control.
The functions of ATACS are as follows:
(a) Train interval control
The train speed is controlled by calculating the
permissible speed from the limited movement
authority of the train, instead of directly indicating the
speed signal as in the present system.
The base procedure for train interval control is as
follows. First, the train location is transmitted by
radio to the ground controller. Next, the ground
controller determines the location to which that train
can be permitted to move (limited movement
8. Conclusion
The above described the applications conditions of
information technology within JNR and JR East and
605
particularly focused on the train control system. In
the case of the control system, “the development of
information and communications technology” and the
“heightening of transport needs” both progressed as
critical features of the era and the history of this
development was emphasized in this paper. The
construction of a completely new train control system
was also described.
JR East has developed the D-ATC and DS-ATC,
and is moving forward with the introduction of the
system. Shinkansen and conventional railways
operating with this digital ATC will provide
passengers safer, more comfortable travel. Moreover,
since the new ATC is of an on-board control type, its
entire composition is more compact, which allows for
reductions in construction and maintenance costs. We,
at JR East, are confident that D-ATC and DS-ATC will
become a standard ATC for railway systems and
intend to recommend its introduction in various fields.
We have already finished control run tests of
prototype ATACS. The results of the test show this
system is developed enough to put into actual service.
New train control systems will be developed in the
21st century by applying the latest information and
control technology in place of the conventional
signaling system applied for over 100 years.
Future autonomous train control systems will
consist of an on-board system only, without a ground
system. Each train will communicate directly with
others and each train will control its own brakes
autonomously, based on information from other trains.
ADS technology, information technology and
communication technology is the key to realize the
future train control system.
Dec.1984
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